The present invention relates to the alloying of molten metal and more particularly to the concept of a powder injector for small ladles of the type used in alloying molten metal.
The invention relates to ladles of the type used in foundries or ferro alloying plants, such as generally illustrated in Fadler U.S. Pat. No. 3,486,745. In the past, molten metal is alloy in relatively small ladles, such as a ladle having a capacity of less than about 10 tons. These ladles are heated by external sources, such as electrical induction or gas heating, and, to prevent splashing, a removable lid or cover is employed. Such ladle is illustrated in Fadler U.S. Pat. No. 3,486,745 that is incorporated by reference as background information.
Production of alloys such as ferro silicon magnesium involves the melting of ferro silicon in a relatively small ladle. To introduce the desired amount of magnesium, a large bar or ingot of manganese is lowered into the molten metal, resulting in a substantial amount of magnesium being lost as vapor. Further, the surface area of the large magnesium bar does not facilitate rapid melting and dispersion of the magnesium in the molten ferro silicon. Magnesium powder is substantially cheaper than a magnesium ingot or bar and provides larger surface area for rapid melting of the magnesium and dispersion into the ferro silicon. However, efforts to inject powder into the small ladle results in violent splashing of the molten ferro silicon. The need for a gaseous carrier to inject powder into the molten metal further exacerbates the splashing and violent reaction at the surface of the hot ferro silicon. Consequently, the more expensive magnesium bar or ingot is used in a ferro silicon plant to alloy ferro silicon with magnesium. The same problem is experienced in other metallurgical processes in foundries that experience splashing and violent surface agitation in small ladles caused by alloying powder, including magnesium, calcium oxide, or calcium carbonate, to name only a few. Such foundry ladles normally have covers that are either on or off as shown in Fadler U.S. Pat. No. 3,486,745. To inject powder, the cover is removed and the powder lance is moved into the molten metal causing the aforementioned unacceptable splashing and violent surface agitation of the metal in the ladle.
The present invention relates to a powder injector for a small ladle of molten metal having an exposed upper surface. This powder injector allows powder carried by a gaseous media, preferably nitrogen, through a lance to be injected under the surface of the molten metal, without the problems experienced by splashing and spraying of molten metal from the ladle during the powder injection process. This new powder injector comprises a splash deflector with a cast body of heat resistant material. A downwardly facing lower surface of the body defining an outer periphery is suspended over the upper level of molten metal, whereby the downwardly facing surface is just above the molten metal. The outer periphery of the splashing deflector cast body has a notch to accommodate an elongated powder injection lance with a tubular body extending vertically from above the deflector surface to a position substantially below the molten metal surface and into the molten metal. This lance includes a directional outlet nozzle for directing the powder in a path at a transverse angle to the lance body. The powder and gaseous carrier is maintained below the large lower surface of the deflector body. By suspending both the lance and the splash deflector from a common mechanism, the powder injector can be lowered into the ladle. The periphery may be contoured to match this one side in one embodiment; however, this is not a requirement. The injector can be positioned away from the side or adjacent an opposite side. The downward movement of the deflector and lance is stopped when the surface of the cast body is slightly above the molten metal surface and the lance is below the surface. The lance nozzle directs powder and the gaseous carrier in a path generally bisecting the deflector lower surface, whereby all agitation of the molten metal occurs below the surface of the deflector.
In accordance with an aspect of the invention, the size of the upper surface of metal in the ladle is substantially greater than the peripheral size of the splash deflector. In this manner, the splash deflector and associated lance is suspended above and adjacent to one side of the ladle. Other surface areas of molten metal in the ladle are exposed; however, they are not agitated because the injection of powder occurs below the splash deflector. The lance can be associated with the deflector outside of the body periphery so long as the directional nozzle propels injected powder underneath the deflector. In accordance with the preferred embodiment, a notch is provided in the body of the splash deflector at a position opposite to the position of the ladle side wall matching the deflector. Thus, the injector propels powder toward the covered side of the ladle and under the splash deflector to prevent surface agitation and unwanted splashing of metal from the ladle. Molten metal in the remainder of the ladle is quiescent and can be charged with other alloying agents that do not have the volatile nature of powdered magnesium.
In accordance with another aspect of the invention, the splash deflector, with an internal metal framework, is a separate component from the injector lance. Thus, the lance can be changed before the splash deflector and lance are moved downwardly in unison into the molten metal. A notch in the deflector receives the lance or the lance can be adjacent the periphery of the deflector body. In both instances, the propelled path of the powder is under the deflector.
In accordance with another aspect of the present invention, there is provided a method of injecting powder into a molten metal in a ladle, wherein the molten metal has an upper level with an exposed large shape. Powder is injected into the molten metal by a lance having a position below the upper surface of the metal and injected under the deflector. The powder injection path is covered by placing the splash deflector over the upper level of metal. A lower large surface is above the powder injection path. Consequently, the injected powder and gas carrier cause violent reaction in the body of the molten metal below the surface of the splash deflector and near the injector. The remainder of the molten metal remains quiescent and can be charged with other constituents, if desired. There is no need to remove the splash deflector for injecting of powder into the molten metal.
The primary object of the present invention is the provision of a powder injector for foundry and metallurgical plants using small ladles, which injector allows injection of powder carried in a gas even though such injected constituents cause violent surface reaction of the molten metal.
Yet another object of the present invention is the provision of a powder injector, as defined above, which powder injector includes a large splash deflector, with the powder injected into the molten metal below the splash deflector. The violent reaction is under the deflector.
Still a further object of the present invention is the provision of a method of injecting powder into a molten metal, which method prevents unwanted splashing and loss of the powdered material.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.